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Regulation of alkane degradation pathway by a TetR family repressor via an autoregulation positive feedback mechanism in a Gram‐positive Dietzia bacterium
Author(s) -
Liang JieLiang,
Nie Yong,
Wang Miaoxiao,
Xiong Guangming,
Wang YiPing,
Maser Edmund,
Wu XiaoLei
Publication year - 2016
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13232
Subject(s) - tetr , alkb , biology , biochemistry , alkane , operon , monooxygenase , regulator gene , bacteria , gene , pseudomonas putida , repressor , stereochemistry , genetics , regulation of gene expression , mutant , gene expression , cytochrome p450 , metabolism , chemistry , escherichia coli , catalysis
Summary n‐ Alkanes are ubiquitous in nature and serve as important carbon sources for both Gram‐positive and Gram‐negative bacteria. Hydroxylation of n‐ alkanes by alkane monooxygenases is the first and most critical step in n‐ alkane metabolism. However, regulation of alkane degradation genes in Gram‐positive bacteria remains poorly characterized. We therefore explored the transcriptional regulation of an alk B ‐type alkane hydroxylase‐rubredoxin fusion gene, alk W 1 , from D ietzia sp. DQ 12‐45‐1b. The alk W 1 promoter was characterized and so was the putative TetR family regulator, AlkX , located downstream of alk W 1 gene. We further identified an unusually long 48 bp inverted repeat upstream of alk W 1 and demonstrated the binding of AlkX to this operator. Analytical ultracentrifugation and microcalorimetric results indicated that AlkX formed stable dimers in solution and two dimers bound to one operator in a positive cooperative fashion characterized by a H ill coefficient of 1.64 (± 0.03) [ k D = 1.06 (± 0.16) μM, k D ′ = 0.05 (± 0.01) μM]. However, the DNA ‐binding affinity was disrupted in the presence of long‐chain fatty acids ( C 10– C 24), suggesting that AlkX can sense the concentrations of n‐ alkane degradation metabolites. A model was therefore proposed where AlkX controls alk W 1 expression in a metabolite‐dependent manner. Bioinformatic analysis revealed that the alkane hydroxylase gene regulation mechanism may be common among A ctinobacteria.